Normal vision

Normal vision occurs when the cornea and the lens of the eye work properly to focus light onto a layer on the back of the eye known as the retina. The retina then transmits the information to the brain where it is processed. If the images focus perfectly on the retina, this results in 20/20 vision.

Focusing in front of the retina results in nearsightedness, while focusing behind the retina results in farsightedness. If the cornea is shaped like a football instead of a sphere, you have astigmatism.

When any of these conditions occur, the processed information results in a blurry image.

Normal vision occurs when a properly shaped cornea and the lens of the eye causes light to focus on the retina, resulting in clear vision, up close or far away.

Myopia

In a myopic eye, light rays focus in front of, instead of directly on, the retina. Attempts to see far away objects can result in headaches, eyestrain, and fatigue. Myopia may be genetic and can start as early as childhood. Patients who are nearsighted have several treatment options available to them, including glasses, contact lenses, and refractive surgery.

	Myopia occurs when the cornea is too curved or the eye is too long. This causes light to focus in front of the retina, resulting in blurry distance vision.
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Hyperopia

Farsightedness, also known as hyperopia, causes problems focusing on objects that are close. In a hyperopic eye, light rays do not converge or focus by the time they reach the retina. Patients who are farsighted may experience symptoms such as headaches, eyestrain, and fatigue. Glasses, contacts or refractive surgery can correct this condition.

	Hyperopia occurs when the cornea is too flat in relation to the length of the eye. This causes light to focus behind the retina, resulting in blurry close vision.
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Astigmatism

Astigmatism is the most common vision problem where vision is blurred at all distances. An irregularly shaped cornea or lens causes incoming light rays to focus not on a single point, but on two or more focal points. Individuals with astigmatism may experience vision that is blurry or distorted. Astigmatism can also result in headaches and eyestrain. People of all ages can be affected by this eye condition. Scheduling regular eye exams allow the ophthalmologists to detect astigmatism early. In most cases, laser surgery will remove most of or all of the astigmatism.

	Astigmatism is the result of an irregularly shaped cornea or lens. This causes light to focus on two or more focal points instead of just one, resulting in blurry or distorted vision at all distances.
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Vision after 40

As we age, vision gradually worsens when focusing on objects that are near. This is called presbyopia. Patients with presbyopia come to depend on reading glasses or bifocals to help their eyes focus on objects near to them. Unlike nearsightedness, farsightedness, and astigmatism, conditions related to the shape of the cornea, presbyopia is believed to be caused by an age-related loss of flexibility in the lens of the eye.

Presbyopia may be treated by the use of contact lenses, one that is fit for distance vision, and one that is fit for near vision. This method of treatment is called monovision and causes the brain to favor one eye to see objects that are far away, and the other to see objects that are close.

Presbyopia is an age-related condition caused by a loss of flexibility in the lens of the eye. This causes a lack of focus at close distances.

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